This application is based on the Japanese Patent Application No. 2000-229792, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a lighting device which is attached to a storage box, such as a console box or a glove box, installed to a cabin of an automobile.
2. Description of the Related Art
A storage box, such as a console box or a glove box, is installed to a cabin of an automobile. Such small articles as cassette tapes, CDs and MDs, maps, and others are stored in the storage box. Sometimes a cup holder is incorporated into the console box.
When the cabin is dark at night, for example, the inside of the console box is also dark. Accordingly, it is difficult for a person to take desired small articles out of the box and store them into the box, and to handle the cup holder. To avoid this, a common practice is to illuminate the console box or the like to make it easy to visually confirm them. There is proposed a lighting device as shown in FIG. 8. A lighting device 100 is attached to a position near the upper end of a side wall 110 of a console box. An inside of the console box is illuminated with light emitted from a light emitting diode 101 through a lens 102. With illumination, a cup holder 130, which is located while laterally being spaced from the lens 102, is well confirmed by the eye. Such a lighting device is disclosed in JP-A-9-272377.
In the lighting device 100, the lens 102, shaped like U in cross section, is disposed surrounding the front of the light emitting diode 101. A light emitting surface 105 of the lens 102 is flush with a side wall surface 115 of the console box. Light 120 horizontally emitted from the light emitting diode 101 is incident on a light receiving surface 106 of the lens 102 at a right angle, and introduced into the lens 102 while not being refracted at the light receiving surface 106. The light is not refracted also at a light emitting surface 105 of the lens 102, and as a result, it is radiated in the horizontal direction. Light 121 emitted in a downward slanted direction is incident on the light receiving surface 106 of the lens 102 at an acute angle, and is refracted upward at the light receiving surface 106 and introduced into the lens 102. The light having reached to the light emitting surface 105 is refracted downward at the light emitting surface 105, and radiated in a downward slanted direction.
A distribution of light radiated from the lighting device was investigated by the inventors of the present patent application. The results of our investigation were: a sufficient amount of light was radiated in the horizontal direction. Accordingly, the cup holder beside the lens 102 could clearly be viewed. The light radiated in the downward slanted direction was small in its amount. Accordingly, a lower part (bottom part) of the console box was unsatisfactorily viewed. Thus, the conventional lighting device cannot illuminate the interior of the console box over abroad range with a sufficient amount of light. In other words, a great difference is present between the amount of light emanating from the lens 102 in the horizontal direction and the amount of light emanating from it in the downward slanted direction. Therefore, the conventional lighting device cannot illuminate a broad area within the console box uniformly.
Part of light 122 emitted from the light emitting diode 101 in the downward slanted direction is reflected at the lower end of the lens 102, and radiated from the lens surface 105 in an upward slanted direction. This light dazzles a passenger to give rise to a glare.
A possible approach to illuminate the lower part of the console box with a sufficient amount of light is to attach the lighting device 100 to the lower part of the console box. When this approach is employed, the cup holder is illuminated with an insufficient amount of light, however. The illumination of the inside of the console box over a broad range may be realized by increasing the number of lighting devices. This approach, however, causes the following problems. The number of required component parts is increased. An excessive amount of light is used for the illumination. As a result, the interior of the console box and its vicinal area as well will possibly be illuminated. Additionally, the work to adjust a layout of the lighting devices is essential. This is undesirable in the light of design and assembling.
An additional approach is to attach the lighting device 100 to the upper wall of the storage space, e.g., the glove box. This approach also fails to illuminate the inside of the glove box over a wide range. In particular, it can insufficiently illuminate the articles located at the inner part of the glove box.
Accordingly, an object of the present invention is to provide a lighting device capable of more uniform illumination over a broad range with light with a simple construction. Another object of the present invention is to provide a lighting device capable of efficiently illuminating a lower part (bottom part) or the inner part of a box-shaped container or the like. Still another object of the invention is to provide a lighting device little giving rise to dazzling and glaring.
To achieve at least one of the above objects, there is provided a lighting device attached to a wall, wherein the lighting device has LED light source and a lens, the LED light source is disposed while being confronted with one end part of the lens, the lens includes a light emitting surface arranged substantially parallel to the wall when the lighting device is attached to the wall, and a first light receiving surface, the first light receiving surface receives light that is emitted from the LED light source in a direction slanted with respect to the light emitting surface, and takes a concave surface configured such that a distance from the first light receiving surface to the light emitting surface increases from one end to the other end of the lens.
Light which is emitted from the LED light source while being slanted with respect to the light emitting surface, is refracted by the first light receiving surface and introduced into the lens. The first light receiving surface is not a flat surface parallel to the light emitting surface, but a concave surface configured such that a distance from the first light receiving surface to the light emitting surface increases from one end to the other end of the lens. Accordingly, light that is incident on the first light receiving surface is introduced into the lens at an incident angle and a refracting angle, which are smaller than in a case where the first light receiving surface is parallel to the light emitting surface. Accordingly, the light introduced is directed to a position closer to the other end of the lens on the light emitting surface than in the case where the first light receiving surface is parallel to the light emitting surface. And, an incident angle with respect to the light emitting surface is larger than in that case. As a result, the light is radiated outside through a position closer to the other end of the light emitting surface at a larger refracting angle.
Therefore, in attaching the lighting device of the invention to a container or the like, the lens may be mounted on the side wall of, for example, a console box in a state that one end of the lens is as the upper end and the other end of the lens is as the lower end. In this case, the lower part (bottom part) within the console box is effectively illuminated with light that is radiated outside from a position closer to the other end than the light emitting surface at a large refracting angle.